RIKEN Center for Sustainable Resource Science (CSRS), Yokohama, Japan.
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.
J Exp Bot. 2024 Oct 30;75(20):6489-6499. doi: 10.1093/jxb/erae303.
Non-specific phospholipase C (NPC) is an emerging family of lipolytic enzymes unique to plants and bacteria that play crucial roles in growth and stress responses. Among six copies of NPC isoforms found in Arabidopsis, the role of NPC3 remains elusive to date. Here, we show that NPC3 is a functional non-specific phospholipase C involved in tolerance to tunicamycin (TM)-induced endoplasmic reticulum (ER) stress through the synthesis of phosphocholine (PCho), a reaction product of NPC3. The npc3 mutant exhibited reduced sensitivity to TM treatment. Recombinant NPC3 possessed pronounced phospholipase C activity that hydrolyses phosphatidylcholine (PC). The hyposensitivity of npc3 to TM treatment was complemented by exogenous PCho, suggesting that NPC3-catalysed PCho production is involved in TM-induced ER stress tolerance. NPC3 was localized at the ER and was predominantly expressed in the roots, and it was further induced by TM-induced ER stress. Intriguingly, npc3 mutants showed a markedly reduced PCho content in shoots under ER stress. Our results indicate that ER stress induces NPC3 to produce PCho, which is involved in TM-induced ER stress tolerance.
非特异性磷酯酶 C（NPC）是一个新兴的脂解酶家族，仅存在于植物和细菌中，在生长和应激反应中发挥着关键作用。在拟南芥中发现的 6 种 NPC 同工酶中，NPC3 的作用至今仍不清楚。在这里，我们表明 NPC3 是一种功能性的非特异性磷酯酶 C，通过合成磷酰胆碱（PCho）参与了对衣霉素（TM）诱导的内质网（ER）应激的耐受，PCho 是 NPC3 的反应产物。npc3 突变体对 TM 处理的敏感性降低。重组 NPC3 具有明显的磷酯酶 C 活性，可水解磷脂酰胆碱（PC）。npc3 对 TM 处理的低敏感性可以通过外源性 PCho 来补充，这表明 NPC3 催化的 PCho 产生参与了 TM 诱导的 ER 应激耐受。NPC3 定位于内质网，主要在根中表达，并进一步被 TM 诱导的 ER 应激所诱导。有趣的是，npc3 突变体在 ER 应激下表现出明显降低的 shoots 中的 PCho 含量。我们的结果表明，ER 应激诱导 NPC3 产生 PCho，参与 TM 诱导的 ER 应激耐受。
